Metal material, ceramic material, polymeric material, and electronic material are four main classes in current material science field. Each material owns its specific properties for certain use. For example, the polymeric material has advantages of its readily processing, robustness, resilience, corrosive-resistance, electrical-insulation, and low cost but has disadvantages of poor heat-resistance and mechanical property. The ceramic material has advantages of stiffness, low activity, thermal stability but has disadvantages of heavy and brittleness. It will develop a new material having new properties if someone takes advantages of one material for compensating shortcoming of another material. Such a concept attracts people's attention to further investigate an organic-inorganic material hybrid material.
Conventional composite has a domain in the order of microns to millimeters. In such a composite the organic or inorganic component mainly plays a role for varying a structure or function of the composite. Its preparation mainly comprises a physical blending. Additionally, the hybrid material is prepared by sol-gel or self-assembly process to hybridize the organic and inorganic material. For example, incorporation of organic material into inorganic master material will improve the inorganic material's brittleness and could render the inorganic material colors. Alternatively, incorporation of inorganic material into organic master material will improve the organic material's strength, heat-resistance and hygroscopicity. Thus, new material having novel properties will be developed through molecular design.
Conventional organic-inorganic material should always be heated at elevated temperature to achieve its complete cross-linking and remove moisture or solvent contained in the reaction system. Silica/polyimide hybrid material prepared from sol-gel process has been extensively investigated due to its excellent heat-resistance. Such a heat-resistance is useful especially in the IC production requiring to process at an elevated temperature. One process for producing the silica/polyimide hybrid material comprises the steps of physically mixing poly(amic acid) solution with tetraethyl orthosilicate (TEOS) solution, spin-coating and then heated and cured to form a film. However, a phase separation will occur in the reaction system. To avoid the phase separation, an approach is to introduce coupling agent into the system since coupling agent will provide a bonding between two immiscible materials. Analysis to the silica/polyimide hybrid material resides in its optical property, a ratio of the organic to inorganic material, and hygroscopicity. There are many kinds of silica/polyimide hybrid material including water-soluble hybrid material, stiff hybrid material, and photo sensitive hybrid material, each of which has different use.
Increasing with the maturation for developing the silica/polyimide hybrid material, more research to the silicon-based material has been conducted. Among them, poly(silsequioxane) has been attracted due to its low dielectric index. With decreasing of line width on integrated circuit board, there exists a problem of signal transmission delay. To decrease the effect of signal delay [Resistance Capacitor (RC) delay], one method is to decrease resistance by using copper process and another method is to decrease capacitor formed between two conductive lines by using insulator layer having low dielectric index. Thus, development of material having low dielectric index becomes a major subject in material science field recently. Among them, poly(silsesquioxane) has a dielectric index of from 2.6 to 2.9, which is far less than that of silica (i.e. dielectric index of 4.0).
Generally, poly(silsesquioxane) is prepared from a hydrolysis of trifunctional silane monomer and then condensation in which the functional groups are the same or different and selected from chloro, methoxy, or ethoxy. Molecular weight, structure of the condensing product and the number of terminal functional groups present in the condensing product are greatly affected by reaction conditions such as properties of monomer, reaction temperature, kinds of catalyst and solvents. Among poly(silsesquioxane), poly(methyl silsesquioxane)(PMSQ) is most popular and becomes an excellent low dielectric material since it has a dielectric index of 2.7, low hygroscopicity, excellent heat-resistance, and mechanical strength. However, PMSQ exhibits poor adhesion to silicon wafer and is brittle thus its use is limited. Introduction of organic polymer into PMSQ will overcome such disadvantages.
Using poly(silsesquioxane)/polyimide hybrid material to prepare low dielectric film is known. It is now describing as follows.    (1) Diamine is first reacted with dianhydride to form poly(amic acid). Then methyl trimethoxy silane monomer (MTMS, a starting monomer for poly(silsesquioxane)) and coupling agent are added into the poly(amic acid) solution to allow the MTMS hydrolyzing and condensing catalytically by using acidic property of the poly(amic acid). Finally, the resultant solution is coated on a substrate and cured to form a film. In this method, although addition of coupling agent provides a bonding between inorganic material and organic material, there still exists a problem of phase separation. This is because that it is difficult to control the MTMS reaction condition precisely, thus it is difficult to control the content of Si—OH and then results in poor property of the film due to phase separation. Moreover, a byproduct methanol still remains in the reaction system.    (2) Poly(silsesquioxane) and poly(amic acid alkyl ester) are prepared separately, and then mixed with addition of coupling agent to subject to a hybridization. Finally, the resultant hybrid material solution is coated on a substrate and cured to form a film. In this method, poly(amic acid alkyl ester) is used the precursor for polyimide, other than poly(amic acid). By using poly(amic acid alkyl ester) as the precursor for polyimide, it can be dissolved in more kinds of solvents but it also limits the ratio of organic material to inorganic material. For example, in such method, proportion of the polyimide is at most of 30% and thus it is impossible to use polyimide as a master material to produce a hybrid material.
Summary, preparation of low dielectric film and optical waveguide material from poly(silsesquioxane)/polyimide hybrid material has the following questions: (1) evenly dispensing of the organic into inorganic materials is difficult and thus easily results in phase separation; (2) only one of organic material and inorganic material could be used as a master material due to the limited ratio of the organic material to inorganic material.
To overcome the disadvantages of the conventional organic-inorganic material, the present inventors have investigated a process for producing a hybrid material and thus completed the present invention.